Graham Jones of timeanddate.com joins with Deborah Byrd of EarthSky to explain why the December 4-5 quarter moon – aka a ‘half moon’ – is more than 50% illuminated. Plus, we share some key moon dates for 2024, from the closest moon to the shortest lunar month. Original article from timeanddate.com on November 27, 2023. Reprinted with permission. Edits by EarthSky.

Quarter moon or half moon?

From our perspective on Earth, the 3rd quarter moon on the night of December 4-5, 2023, will be the most-illuminated quarter moon of this year. It’ll be 50.137% lit, as seen by us on Earth.

A quarter moon looks half-illuminated in Earth’s sky. Some people even call it a half moon. And we in astronomy often say a quarter moon – aka a half moon – appears from Earth to be 50% illuminated.

But it’s not true. Instead, every quarter moon (half moon) is always slightly more than 50% illuminated.

And the December 4-5, 2023, quarter moon is the most illuminated of all the quarter moons this year.

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A fraction more than half?

Who knew that a quarter moon is always more than half illuminated? That’s not common knowledge, even among astronomers. But it’s true.

Here’s why. In astronomy, we define the instant of quarter moon as when the sun and moon are separated by 90 degrees, as seen from Earth.

But, in order for the moon to appear exactly 50% illuminated for an observer on Earth, the sun and Earth must be separated by 90 degrees, from the perspective of the moon.

See? It’s a tiny difference, but a measurable one. From Earth, at every quarter moon, a fraction more than 50% of the Earth-facing side of the moon is illuminated.

Not to scale

The illustration above is a very rough representation of the triangle formed by the sun, Earth, and moon. In reality, the distance from Earth to the moon is about 30 times the diameter of Earth. The distance from Earth to the sun, meanwhile, is around 12,000 times Earth’s diameter.

In other words, although our not-to-scale illustration shows a small and compact triangle, the actual triangle is extremely long and narrow.

As the moon travels along its orbit, the moment when it is exactly 50% illuminated comes around 20 minutes after the moment of 3rd quarter, or before the moment of 1st quarter.

(Our illustration ignores an effect called parallax, where the moon’s position differs by a tiny amount depending on your observing location on Earth. Moon phase calculations are based on the centers of the Earth and moon.)

December 5 is also the farthest quarter moon

Although the 3rd quarter moon on December 5 won’t look different from any other quarter moon, it will also be the farthest quarter moon from Earth in 2023. This is not a complete coincidence: as the Earth-moon distance gets larger, the percentage of the moon’s face that is lit up increases.

Similarly, it is no coincidence that December 5 falls near perihelion (early January), when Earth is closest to the sun. A smaller Earth-sun distance also leads to a greater percentage of the moon’s face being lit up.

Lesser-known moon dates for 2024

The moon’s orbit around Earth is never the same from one lunar month to the next, leading to events such as supermoons and micromoons.

So, again, in 2023, the most-illuminated quarter moon will be the 3rd quarter moon of December 5. And, in 2024, the most-illuminated quarter moon will be the 3rd quarter moon of December 22.

Here are seven lesser-known lunar events for 2024.

January 25: Longest moon phase of 2024. There will be 8.225 days between full moon on January 25 and 3rd quarter moon on February 2.

March 10: Closest moon of 2024. The most extreme Earth-moon distances occur at new moon or full moon. At new moon on March 10, the moon will be 221,764 miles (356,895 km) away.

May 30: Shortest lunar month of 2024. The moon will cycle through all its phases – from 3rd quarter moon on May 30 to 3rd quarter moon on June 28 – in 29.195 days.

August 19: Shortest moon phase of 2024. The moon will take 6.625 days to wane from full moon on August 19 to 3rd quarter moon on August 26.

October 2: Farthest moon of 2024. At new moon on October 2, the distance to the moon will be 252,597 miles (406,516 km).

November 23: Longest lunar month of 2024. It will take the moon 29.868 days to go from 3rd quarter on November 23 to 3rd quarter on December 22.

December 22: Most-illuminated quarter moon of 2024. And so it comes around again!

Bottom line: Some quarter moons are fuller than others! The most-illuminated quarter moon of 2023 is on December 5. This happens when the moon is in a slightly different position in its orbit … a little bit after 3rd quarter, or a little bit before 1st quarter. Learn more unique moon dates for 2024.

The post 2023’s most-illuminated quarter moon is tonight first appeared on EarthSky.

The crest of the November 2023 full moon will fall at 3:16 a.m. CT (9:16 UTC) on Monday, November 27. So – for the Americas – the fullest moon will come overnight on Sunday, November 26. And the fullest moon for Asia will fall on November 27. But all of us will see a bright, nearly full moon this weekend. As a bonus, this weekend’s moon is near the bright planet Jupiter in the night sky.

On the night of full moon – November 26-27 – the bright, round full moon will be climbing in the east, as night falls. And we’ll all find the moon on both Sunday and Monday nights glowing high in the south near midnight and dropping low in the west near sunrise before dawn.

Full-moon is a whole-Earth event. And every full moon is opposite the sun, rising when the sun sets and setting when the sun rises. At full moon, the sun, Earth, and moon form a line in space, with Earth in the middle. It’s at this time that the moon’s fully lighted hemisphere – its day side – faces Earth most directly.

And Jupiter? It’s no accident this mighty planet is near this month’s full moon. Earth passed between Jupiter and the sun in November 2023. A full moon is opposite the sun. And Jupiter was opposite the sun last month, at its opposition. So, as Earth and mighty Jupiter have moved on in their orbits around the sun, Jupiter is still nearly opposite the sun as seen from Earth. So Jupiter and this weekend’s full moon appear together in the sky.

The 2024 lunar calendars are here! Best Christmas gifts in the universe! Check ’em out here.

November full moon is Beaver or Frosty Moon

All the full moons have popular nicknames. If the full moon in November falls before November 7, it’s called the Hunter’s Moon.

Otherwise, as in 2023, you can call November’s full moon the Beaver Moon, or Frosty Moon. In November, North American beavers are preparing their dens – and stocking up on food – for the coming cold months.

We also hear the name Digging Moon for this November full moon, because of the last chances for seasonal foraging by forest animals.

The moon’s path across the sky

In the Northern Hemisphere, the sun travels across the southern sky each day in a short, low arc. So the full moon, being opposite the sun in the sky, travels in a long, high arc across the night sky. Now consider the moon’s path six months ago or six months from now. A May full moon travels in a short, low arc, while the May sun moves in a long, high arc. See? At full moon, the sun and moon are opposite each other in space.

Why is the full moon so bright?

All full moons are bright. And their strong glow lightens the sky enough to blot out all but the bright planets and brightest of stars.

There are two major reasons the full moon is so bright. First and most obviously, a full moon isn’t a point of light, like a star or a planet. It covers a much-larger area of our sky, and so reflects more of the sun’s intense light. But secondly, and most importantly, the sun is so bright. It’s some 400,000 times that of the moon. And moonlight is just reflected sunlight. So the moon isn’t really bright in and of itself. In fact, the moon’s surface has a relatively low reflectivity, similar to that of asphalt.

If the moon had a reflectivity matching that of snow, the full moon would be over five times brighter!

November full moon in Taurus

The November full moon can lie in front of one of three constellations of the zodiac. Most years, as it does this year, it falls in Taurus the Bull. But it can also be in Aries the Ram as it will be in 2025.

Very infrequently, November’s full moon lies in the sprawling constellation just southwest of Taurus, called Cetus the Whale.

The moon is roundest on the day that it’s full. But the day before and after, it appears almost, but not quite round and full in our sky.

Bottom line: The November full moon will fall overnight on November 26-27, 2023. Bright Jupiter will be nearby. And the Pleiades star cluster will lie in the moon’s glare.

The post November full moon and Jupiter this weekend first appeared on EarthSky.

Moon phase is a whole-Earth phenomenon

Everyone looking up at the moon from any spot on the globe sees the same moon, in more or less the same phase. So why might photos of the moon taken on a single night – but from different parts of Earth – look different?

And also, here’s a related question. Why does the moon look different – even from the same spot – over the course of a single night?

Let’s take the second question first. The moon’s orientation with respect to your horizon shifts throughout the night because we live under a curved dome of sky. Think of the curved arc traveled by the sun during the day. The moon and the stars follow similarly curved paths.

The illustration below shows the curved line traveled by the stars and the moon, as they traverse Earth’s dome each night (or day). And that is because Earth’s rotation under the sky causes the stars and moon to move westward throughout the night. However, the moon’s motion in its orbit around Earth each day is eastward, in front of the background stars.

The 2024 lunar calendars are here! Best Christmas gifts in the universe! Check ’em out here.

How the moon changes over hours

Overnight – or even in a few hours – you can notice the appearance of the moon changes.

How the moon changes between hemispheres

So now, why do people in different parts of the globe, see the same moon phase, but it appears different? People in the Northern and Southern Hemispheres see the moon oriented differently from one another. It’s not a change in phase. It’s a change in the orientation of the moon with respect to your horizon. The differences can be hard to comprehend!

For one thing, observers in the Northern and Southern Hemispheres see the moon apparently upside-down with respect to each other. You can see that, if you scrutinize the moon’s features in the image below.

Also, notice that from the Northern Hemisphere, a waxing moon (from new moon to full moon) increases its phase from right to left. Meanwhile, from the Southern Hemisphere, a waxing moon (from new moon to full moon) increases its phase from left to right.

Have you ever been to the southern hemisphere Ashes??
Ever see the Southern Cross? Sigma Octantis?
The sun moving from right to left each day?
The stars moving clockwise each night?
The moon phases move from left to right over 28 days?#SouthernHemisphereDisprovesFlatEarth pic.twitter.com/pfESD411yH

— Rozzie (@RozzieVox) November 18, 2019

Why so different? Think of the moon’s path across your sky. Just picture yourself standing there, looking at it. From the Northern Hemisphere, we look generally southward to see the moon (or sun) crossing our sky. From the Southern Hemisphere, people look generally northward to see the moon (or sun) crossing the sky.

Can you see why that shift in your orientation on the globe would cause you to see the moon differently?

A final thought

What we on Earth call moon phases are really about sunrise and sunset on the moon. Astronomers call the line between light and dark on the moon the terminator line. That’s the line of sunrise or sunset on the moon, and it shifts, just as the line of sunrise and sunset on Earth is constantly shifting.

Also, Earth spins relatively fast, approximately once every 24 hours. The moon spins on its axis only once each earthly month, and its line of sunrise/set moves slowly. It’s wonderful fun to beg or borrow a telescope for a night when the moon is up … and watch for yourself over several hours as the shadows slowly shift on the moon, as the lunar sunrise or sunset slowly creeps across the moon’s face.

Of course, it’s also a great way to clear the mind!

Bottom line: The moon shows one phase to the Earth at the same time, but our different perspectives due to where we are on the globe can make the moon appear differently in our sky.

Want more? Visit phases and orbits of the moon

The post Do we all see the same moon phase from Earth? first appeared on EarthSky.

When and where to look in 2023: As seen from around the globe, look for the bright, round full supermoon rising in the east at sunset on September 28. It’ll glow highest in the sky near midnight, and drop low in the west before sunrise on September 29. This is the full moon closest to the equinox and so we call it a Harvest Moon.
Crest of the full moon falls at 9:57 UTC (4:57 a.m. CDT) on September 29, 2023. So many will say that the full moon – and the Harvest Moon – falls on September 29. That’s equally true and valid!

The 2023 super Harvest Moon will lie between two bright planets. Golden Saturn will rise over an hour before the full moon and travel ahead of it in the sky through the night. Our solar system’s largest planet, very bright Jupiter, will rise about 90 minutes after the moon. See the chart above. And check Stellarium.org for a precise view from your location.

Harvest Moon isn’t just a name. It denotes a time of year when the full moon – as seen from the Northern Hemisphere – has special characteristics. Find out more about the Harvest Moon below, or check out our video.

Harvest Moon is special

We in the Northern Hemisphere have long called the full moon closest to the September equinox by the name Harvest Moon. That name – Harvest Moon – might be the best known full moon name of the year. This year, the September equinox occurs at 6:50 UTC (1:50 a.m. CDT) on September 23, 2023. The full moon falls about six days later.

What’s special about a Harvest Moon? As seen across Earth, the moon on average rises about 50 minutes later each day, as it orbits Earth. But in mid-to-late September – for mid-latitudes in the Northern Hemisphere – that moonrise time drops to 20 minutes later each day around the time of full moon. The higher the latitude, the shorter the interval between successive moonrises.

September full moon and the ecliptic

Why? It’s because the ecliptic – or path of the sun, moon and planets across our sky – makes a narrow angle with the eastern horizon near sunset, around the time of the autumn equinox. For Northern Hemisphere observers, that means September or October. For Southern Hemisphere observers, it means March or April. The narrow angle of the ecliptic to the evening horizon – around the time of the autumn equinox – gives us the short interval between successive moonrises and the Harvest Moon.

Click here for a printable calendar showing the time of moonrise for your location

And a short interval between successive moonrises means that – for several evenings in a row, around the time of this September full moon – you’ll find a full or nearly full-looking moon low in the east in evening twilight. Before the days of electric lights, the early evening light of this full moon let farmers working in the fields have more time to work, before darkness settled. Hence, the name Harvest Moon.

And, by the way, for the Southern Hemisphere at this full moon, there’s a particularly long interval between successive moonrises!

It’s also a supermoon

Yes, the September full moon is another supermoon. As you might recall, the last three full moons were supermoons as well. In fact, the September Harvest Moon is the last of four supermoons in a row for 2023.

How close is it? The moon will be 224,658 miles (361,552 km) away. Comparatively, the average distance between Earth and the moon is 238,900 miles (384,472 km). So – while the September 28-29 full moon might not look bigger to the eye – it’ll surely look brighter than an average full moon.

And of course since it’s closer than usual it’ll also be pulling harder, via gravity, on Earth’s oceans. People who live near an ocean might notice particularly high tides in the day or so after this full moon.

September full moon lies in Pisces

The September Harvest full moon always lies in front of one of three constellations of the zodiac. Most years, it lies in Pisces the Fish, as it does this year. About every three years, though, it’ll lie in Aquarius the Water Bearer, as it did last year. Very infrequently – once about every 20 years – it’ll fall in the less-familiar constellation lying to their south, Cetus the Whale.

Bottom line: The Harvest Full Moon – and last of four full supermoons in 2023 – happens overnight on September 28-29, 2023, for us in the Americas. This full moon lies in front of the constellation Pisces. And it lies between two planets, very bright Jupiter and golden Saturn.

Want to see 2023’s brightest supermoon? Photos here

Read more: Does a supermoon have a super effect on us?

The post September full moon 2023 is a super Harvest Moon first appeared on EarthSky.

The full super Harvest Moon is coming up overnight on September 28-29, 2023, for us in the Americas. And we know there are lots of superstitions about full moons. Scientists have debunked many, while others are still under study. But here’s one that appears to be true: people do sleep less before a full moon.

That was the conclusion of a 2021 study in the peer-reviewed journal Science Advances.

Scientists at the University of Washington, the National University of Quilmes in Argentina and Yale University conducted the study. They analyzed sleep patterns in two very different locales. First, they studied Toba/ Qom communities of rural Argentina, where people have little to no access to artificial light sources. Then, they studied college students living in downtown Seattle, Washington.

Their results show that, even in urbanized locations where the light of the full moon is drowned by city lights, the phases of the moon still influence people’s sleep patterns.

Do you sleep less before a full moon?

In the not-too-distant past – before the days of electric lights – people would spend more hours outside after dark around the time of a waxing gibbous or a full moon. On those nights, the moon shines in the evening sky as the sun goes down. The full or nearly full brightens the evening sky. It provides extra light for human work and play to extend past daylight hours.

The best-known example of a full moon that lights up human activities is probably the full Harvest Moon. It happens in the autumn months when, for several nights in a row around the time of full moon, there’s no long period of darkness between sunset and moonrise.

And, of course, autumn is also harvest time, so farmers would gather in their crops by the light of the moon.

Read about this year’s Harvest Moon

How our ancestors slept

In preindustrial society, humans’ lives revolved around sunrise and sunset. When it was dark, it wasn’t safe outside anymore to hunt or gather food.

But with the advent of artificial lighting, humans could and quickly did change their sleep-and-wake patterns. Now people are up – working and playing – at all hours of the day and night.

And yet, as with humans of old – and as with animals living in the wild – we modern humans are still subject to circadian rhythms. Those 24-hour cycles dictate when wakefulness and sleep should occur.

And the cycles are tied to light, with sunlight waking diurnal creatures and sending nocturnal animals back to their lairs.

How people sleep now

Participants in the 2021 sleep-moon study wore wristwatches that monitored their sleeping and waking.

Scientists who participated in the study were able to show that the oscillation patterns in people’s sleep coincided with moon phases. These researchers – led by University of Washington professor of biology Horacio de la Iglesia – reported that from three to five days leading up to a full moon, people tended to go to bed later in the evening and sleep less overall.

The study showed that whether the people are in a dark rural environment or an urban environment, where moonlight can’t compete with the lights of the big city, their test subjects still followed the pattern of falling asleep later and sleeping less in the week leading up to full moon.

So – even if you’re not aware of the moon phase – it likely still has an effect on you.

What did they learn?

People in the study groups fell asleep up to a half hour later on full moon nights in contrast to new moon nights (which are nights with no moon at all). And they slept for up to an hour less on full moon nights than during new moon.

The more rural the people in the study were, the stronger the effect. But those in the big city still responded to the moon’s influence.

In the nights following a full moon, a now-waning moon will rise later in the evening, often after most people have already fallen asleep. On those nights, the researchers found no effect via moon phase on the sleep patterns of people studied.

Future sleep researchers will probe questions of the full moon’s effect on our circadian rhythms.

For now, if you find yourself tossing and turning on nights leading up to a full moon, no need to stress. And if – around the time of full moon – it seems as if you’re going to bed later, and sleeping less overall … don’t stress! This study has your back.

Bottom line: A new study shows that – whether you live in a rural or urban environment – your sleep patterns might be affected by the full moon. On the nights leading up to full moon, people fall asleep later and sleep less overall.

Source: Moonstruck sleep: Synchronization of human sleep with the moon cycle under field conditions

Via University of Washington

The post Do you sleep less before a full moon? Research says yes first appeared on EarthSky.

Did you catch the full supermoon on August 1, 2023? If you didn’t see it, don’t worry, you have two more chances coming up! At the end of August we will have another full supermoon (which is also a blue supermoon). And September will have a supermoon, too. For now, though, enjoy the video above, or, if you prefer, these terrific pictures of the August 1 supermoon from the EarthSky community. Thanks to all who submitted!

The photos are still coming in! See additional photos of the August 1 supermoon here.

August supermoon photo gallery

More full moon photos

Bright full supermoon on August 1

Full moon brightness

Bottom line: Enjoy these great photos of the August supermoon. It’s the 2nd of four supermoons in a row. August will have one more supermoon and September will have one.

The post August 1 supermoon: Fav photos from our community first appeared on EarthSky.

Did you see the full supermoon on July 2-3, 2023? If not, don’t worry, you have three more chances coming up! August will have two supermoons (including a blue supermoon) and September will have one supermoon. In the meantime, enjoy these fabulous pictures of July’s supermoon from our readers.

July supermoon photo gallery

More full moon photos

Full moon photos on July 3

Full moon brightness

Bottom line: Enjoy these great photos of the July supermoon. It’s the first of four supermoons in a row. August will have two supermoons and September will have one.

The post July supermoon photo gallery from our readers first appeared on EarthSky.

When to watch in 2023: Overnight of July 2-3.
Where to look: Look for the bright round moon in the east today at evening, highest in the sky around midnight, and in the west before sunrise tomorrow morning.
Crest of the full moon falls at 11:39 UTC (6:39 a.m. CDT) on July 3. So, if you live in either North or South America, your fullest moon hangs somewhere above the western horizon just before sunrise tomorrow morning.

All full moons rise along the eastern horizon near sunset, and set along the western horizon near sunrise. They are visible all night. At full moon, the sun, Earth and moon are aligned in space, with Earth in the middle. The moon’s day side – its fully lighted hemisphere – directly faces us. That’s why the moon appears full. Note that the moon will look full and round the day before and the day after it reaches its fullest.

It’s the Buck Moon

All the full moons have names. Popular nicknames for the July full moon include the Feather Molting Moon and the Salmon Moon, but Buck Moon is the most common. At this time of year, the antlers of male deer grow rapidly, sometimes to impressive sizes. Hence, the name Buck Moon. Some Native Americans used the names Thunder Moon, Berry Moon and Raspberry Moon.

Read more: Full moon names by month and by season

Read more: Traditional full moon names and their meanings

It’s also a Supermoon

Also, this July’s full moon is a supermoon because it occurs near its closet orbital point to Earth. Does a supermoon appear larger than ordinary full moons?

While it’s true experienced observers do say they can detect a difference, you’d have to be a very keen observer to notice it. Truly, most of us can’t tell any difference in the size of a supermoon and an ordinary full moon.

But … do supermoons look brighter than ordinary full moons? Yes! By a noticeable amount. That’s because a supermoon exceeds the disk size of an average-sized moon by up to 8% and the brightness of an average-sized full moon by some 16%. And then, it exceeds the disk size of a micro-moon (a year’s most distant and therefore smallest full moon) up to 14% and the brightness of a micro-moon by some 30%. So, if you go outside on the night of July 2-3, there’s the potential you’ll notice the supermoon is exceptionally bright!

July full moon is in Sagittarius in 2023

The July full moon can lie in front of two constellations of the zodiac. The most often one is Sagittarius the Archer. The second is the constellation to Sagittarius’ east, Capricornus the Sea Goat. This full moon glows in front of the central part of the Teapot asterism. Because of the bright moonlight, the eight stars comprising the Teapot will be difficult to see with the unaided eye.

This July full moon mimics December sun

Because a full moon more or less stays opposite the sun, the full moon’s nighttime path mimics the sun’s daytime path from six months ago, or six months hence.

This full moon is the one closest to the June solstice – happening twelve days after it – so this full moon follows nearly the same path across the sky as the December solstice sun. The December solstice is the Northern Hemisphere’s winter solstice. So, the moon’s trek on the nights around this July’s full moon resembles the low path of the winter solstice sun.

North of the Arctic Circle, the wintertime sun never climbs above the horizon. Neither will this July’s full moon.

Meanwhile, in the Southern Hemisphere, the moon’s path across the sky will mirror that of the high summer solstice sun.

And, south of the Antarctic Circle, the moon will be out for 24 hours around the clock, simulating the midnight sun of summer.

Arc of the July full moon, Northern Hemisphere

The moon’s arc across our sky varies from month to month and from season to season. Every full moon rises somewhere along the eastern horizon, opposite the sun as it sets in the west. And every full moon arcs across the sky throughout the night and sets along the western horizon around dawn. For us in the Northern Hemisphere, in most years the arc of the June’s full moon is lower than the paths of the full moons since December. However, this year, the July 3rd full moon arcs slightly lower because it falls closer to the June solstice than the June 4th full moon.

Arc of the July full moon, Southern Hemisphere

For those in the Southern Hemisphere, the full moon’s arc across the sky is climbing higher with each successive month since December, reaching its highest at the full moon falling closest to the June solstice, which occurs sometime from mid-June through early July. In 2023, even though the June 4th full moon is close to the solstice, the July 3rd full moon is closer.

Bottom line: The July full moon – the Buck Moon – falls overnight tonight, reaching its fullest at 11:39 UTC (that’s 6:39 a.m. CDT) tomorrow night. It’s also a supermoon.

The post July full moon is the Buck Moon and a supermoon first appeared on EarthSky.

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When to watch in 2023: Before sunrise and after sunset on May 5.
Where to look: Look for the bright round moon low in the southwest before sunrise, and low in the southeast after sunset on May 5. It appears full during the nights of May 4 and May 5.
Crest of the full moon falls at 17:34 UTC on May 5, 2023. That’s 12:34 p.m. CDT on May 5 in central North America. So, if you live in central North America, your fullest moon falls mid-way between sunrise and sunset on May 5 when it is on the other side of Earth, and, therefore, can’t be seen. The rising moon in the southeast on that morning will resemble the setting moon in the southwest that evening.

A penumbral lunar eclipse in central Asia

This full moon coincides with a penumbral eclipse of the moon. The eclipse is not visible in the Americas, but it is visible in central Asia. Since the moon will not lie in the dark umbral shadow, but in the lightly shaded penumbral shadow instead, the eclipse event might not be easily noticeable. During the eclipse, the full moon lies in Libra the Scales next to the star Zubenelgenubi.

Moon looks full over 3 nights

At full moon, the sun, Earth, and moon align in space, with Earth in the middle. The moon’s day side – its fully lighted hemisphere – faces us. That’s why the moon looks full. Note that the moon will look round for a day or two around full moon. Because the May full moon occurs near mid-day on May 5, the moon will look full on the overnights of May 4, 5, and 6.

It’s the Flower Moon

All the full moons have nicknames. Popular names for May’s full moon include the Planting Moon and the Milk Moon, but the Flower Moon is the most common. As you might expect, the name Flower Moon recognizes the blooming of wildflowers and garden flowers, many giving an enchanting appearance in the light of May’s full moon.

Arc of the May full moon

The moon’s arc across our sky varies from month to month and from season to season. Every full moon rises along the eastern horizon, opposite the sun as it sets in the west. Every full moon arcs across the sky throughout the night and sets along the western horizon around dawn. For us in the Northern Hemisphere, the arc of May’s full moon is lower than the paths of the full moons since December, but higher than the next one in June.

For those in the Southern Hemisphere, the full moon’s arc across the sky is climbing higher with each successive month since December, and will continue to do so until the full moon nearest the June solstice.

The May full moon is in Libra

As seen from the Americas, the full moon on the morning and evening of May 5 is located in the direction of the constellation Libra the Scales. It glows near Libra’s “surprise” star all night. That surprise star is the moderately bright Zubenelgenubi. Zubenelgenubi is a surprise star because people with keen eyesight see it as two stars, and binocular users readily catch its double star nature. Also, on the evening of May 5, the full moon lies close to the red star Antares in Scorpius the Scorpion.

Bottom line: The May full moon occurs near mid-day today, May 5. The moon looks full on the overnights of May 4, 5, and 6.

The post May full moon is the Flower Moon first appeared on EarthSky.

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New moon – when the moon passed between the Earth and sun, causing the April 20 hybrid eclipse – was early this morning. And after every new moon comes a young moon, a slim crescent in the west after sunset. Occasionally – when the moment of new moon happens around midnight by your local clock – you have a chance to see a very young moon, one less than 24 hours old. That’s the case, for some of us, tonight (April 20, 2023).

Seeing such a young moon is a rare delight. At such times, the moon is still close to the sun along our line of sight. In other words, it’s close to the sunset. And its lighted portion is turned almost entirely away from us. It’s a fragile illuminated crescent moon, maybe the thinnest crescent moon you’ve ever seen.

Will you see a very young moon on April 20, 2023? It depends on where you are on Earth’s globe, and on your sky conditions. If you do catch it – and have a photo – please submit it to EarthSky Community Photos.

Young moon on April 20, 2023?

On April 20, new moon happens at 4:12 UTC (12:12 a.m. EDT). This particular new moon passed in front of the sun, creating an unusual hybrid solar eclipse, early in the day on April 20.

This evening (the evening of April 20) – fresh from the eclipse – the young moon, less than a day old, will pop into view in the west after sunset for people who are in North America – and who are in the Eastern, Central, Mountain and Pacific time zones.

Why so specific? There are two things to consider. First, the angle of the ecliptic, or path of the sun, moon and planets. Second … timing.

Angle of the ecliptic. Here’s why it needs to be Northern Hemisphere, not Southern Hemisphere, to see tonight’s young moon. At this time of year, in the Northern Hemisphere, the ecliptic is making a steep angle to the evening horizon. That steep angle carries the moon high above the sunset. Meanwhile, from the Southern Hemisphere, the ecliptic makes a narrow angle with the evening horizon in April. And that narrow angle carries the moon to one side of the sunset, keeping it closer to the horizon. A young moon closer to the horizon is tough to see, because it’s buried in the twilight glare.

Timing. Now consider, for example, London on April 20. London time is just an hour ahead of UTC. So … new moon falls at +4 UTC, or ~5 a.m. London time (“~” means “approximately”). And that means that – on April 20 – the moon around sunset will be just under 15 hours old (5 a.m. to 8 p.m. = 15 hours), as seen from London. And it’s probably not possible to see a 15-hour-old moon with the unaided eye (though some have claimed to have seen it!).

But – by the time of sunset on April 20 as seen from New York City – the moon will have gotten farther from the sun in our sky. It’ll be a slightly older moon, setting longer after sunset. New York City is four hours behind UTC, when daylight time is in effect. So new moon falls at 12:12 a.m. EDT in NYC on April 20. And sunset in NYC on April 20 falls ~7:30 p.m. EDT. And that means that – on April 20 – the moon around sunset will be ~19 hours hours old (12:12 a.m. to 7:30 p.m. = ~19 hours), as seen from NYC … old enough to catch in the west after sunset!

And so on across the various time zones of the continental U.S. Those in the Central time zone will see a young moon ~20 hours old. Those in Mountain time will see a moon ~21 hours old. Those in Pacific time will see a moon ~22 hours old. All see-able, and all less than a day old!

So will you see it? Maybe. You’ll need to look toward an unobstructed horizon, shortly after sunset. Clouds, trees or tall buildings could hide the moon from view. Here’s a tip. As soon as the sun is safely over the horizon, start scanning the western horizon for a sliver of the moon. Use binoculars to scan, if you have them. If you can’t find the crescent moon, look for a surprisingly bright point of light deep in the bright evening twilight. That’ll be Mercury, which is several degrees away from the thin crescent moon on April 20, and might help you spot it.

Trying is always fun. And, if you do see it, the moon on April 20 will be so, so beautiful.

And, just remember, the April 20 young moon will soon follow the sun below the western horizon.

For a more precise view from your location try Stellarium-web.org.

Check here for precise times of the sunset and when the moon sets at your location.

What’s the youngest moon it’s possible to see?

Definitely, it’s rare to see a moon within about 24 hours of the new phase. But it turns out, if you use optical aid, you can see the moon all the way until the moment of new moon. However, always avoid looking directly at the sun!!

On July 8, 2013, a new record was set for the youngest moon ever photographed (see photos below). Thierry Legault – shooting from in Elancourt, France – captured the July 2013 moon at the precise instant it was new. Or most nearly between the Earth and sun for this lunar orbit. Legault’s image (below) shows the thinnest of lunar crescents, in full daylight, at 7:14 UTC on July 8, 2013. Legault said on his website:

It is the youngest possible crescent, the age of the moon at this instant being exactly zero. Celestial north is up in the image, as well as the sun. The irregularities and discontinuities are caused by the relief at the edge of the lunar disk (mountains, craters).

Can you see a young moon with your eye alone?

How young a moon you can expect to see with your eye depends on the time of year and on sky conditions. It’s possible to see the youngest moons – the thinnest crescents, nearest the sunset – around the spring equinox. And so you know, the youngest moons will be more of a slight curve rather than a full crescent.

And cameras can catch more than the eye alone.

For example, when Legault captured the image above, the sun and moon were separated only 4.4 degrees – about 9 solar diameters – on the sky’s dome. It is extremely difficult, and risky, to try to capture the moon at such a time because there’s always a risk of unintentionally glimpsing the sun and thereby damaging your eyesight. So don’t try it, unless you know what you are doing!

Thierry Legault used a special photographic setup to capture this youngest possible moon. He wrote:

In order to reduce the glare, the images have been taken in close infrared and a pierced screen, placed just in front of the telescope, prevents the sunlight from entering directly in the telescope.

The record for seeing a very young moon

A longstanding, though somewhat doubtful, record for youngest moon seen with the eye is by two British housemaids. They said they saw the moon 14 3/4 hours after new moon in the year 1916.

Stephen James O’Meara achieved a more reliable record in May 1990. When he saw the young crescent with the unaided eye 15 hours and 32 minutes after new moon.

The record for youngest moon spotted with the eye using an optical aid passed to Mohsen Mirsaeed in 2002, who saw the moon 11 hours and 40 minutes after new moon. Wow!

But Legault’s photograph at the instant of new moon? That record can only be duplicated, not surpassed.

Tips for observing very young moons

Young moons are located some distance east of the sun on the sky’s dome (because the moon always moves eastward in orbit). Young moons appear to our eye as exceedingly slim crescents. And likely illuminated by earthshine, seen low in the western sky for a brief interval after sunset.

No matter where you are, remember to wait until the sun has completely set before scanning the horizon with optical aid! You’ll also need a flat, clear horizon to the west. Start looking shortly after the sun disappears. So, when bright twilight still fills the western sky look for the infant moon that’s barely illuminated!

And, of course, optical aid enhances your young moon possibilities even more.

Bottom line: Occasionally you get the chance to look for a very young moon, less than 24 hours old. On April 20, 2023, if you are in North America where the timing – an angle of the ecliptic – is right, and you live anywhere in the Eastern, Central, Mountain and Pacific time zones, look for the young moon just after sunset.

Click here to check out Thierry Legault’s book on astrophotography.

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